Bug 1121935 - Add intrinsic for retrieving the original constructor for typed array instances. r=Waldo

js/src/vm/SelfHosting.cpp

@@ -766,6 +766,24 @@ js::intrinsic_IsConstructing(JSContext *cx, unsigned argc, Value *vp)
     return true;
 }
 
+static bool
+intrinsic_ConstructorForTypedArray(JSContext *cx, unsigned argc, Value *vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    MOZ_ASSERT(args.length() == 1);
+    MOZ_ASSERT(args[0].isObject());
+    MOZ_ASSERT(IsAnyTypedArray(&args[0].toObject()));
+
+    RootedObject object(cx, &args[0].toObject());
+    JSProtoKey protoKey = StandardProtoKeyOrNull(object);
+    MOZ_ASSERT(protoKey);
+    RootedValue ctor(cx, cx->global()->getConstructor(protoKey));
+    MOZ_ASSERT(ctor.isObject());
+
+    args.rval().set(ctor);
+    return true;
+}
+
 // The self-hosting global isn't initialized with the normal set of builtins.
 // Instead, individual C++-implemented functions that're required by
 // self-hosted code are defined as global functions. Accessing these
@@ -844,6 +862,7 @@ static const JSFunctionSpec intrinsic_functions[] = {
     JS_FN("AssertionFailed",         intrinsic_AssertionFailed,         1,0),
     JS_FN("MakeConstructible",       intrinsic_MakeConstructible,       2,0),
     JS_FN("_IsConstructing",         intrinsic_IsConstructing,          0,0),
+    JS_FN("_ConstructorForTypedArray", intrinsic_ConstructorForTypedArray, 1,0),
     JS_FN("DecompileArg",            intrinsic_DecompileArg,            2,0),
     JS_FN("RuntimeDefaultLocale",    intrinsic_RuntimeDefaultLocale,    0,0),
     JS_FN("SubstringKernel",         intrinsic_SubstringKernel,         3,0),